This invention relates to a titanium diboride and/or zirconium diboride base sintered ceramic and a method of producing same.
Sintered ceramics using either TiB.sub.2 or ZrB.sub.2 as the principal component are very high in heat resistance, corrosion resistance, hardness and wear resistance. Accordingly TiB.sub.2 and/or ZrB.sub.2 base sintered ceramics will be very useful, for example, as heat insulating materials and mechanical materials for cutting tools, machine parts, heat engine parts, rocket components, etc. Also it is conceivable to utilize good electrical conductivities of these ceramics.
However, both TiB.sub.2 and ZrB.sub.2 are poor in sintering activity. If TiB.sub.2 or ZrB.sub.2 alone is sintered the sintered body is very brittle and low in deflective strength. Therefore, various additives have been tried for improving the mechanical properties of TiB.sub.2 or ZrB.sub.2 base sintered ceramics and also other metal diboride base sintered ceramics. For example, there are the following proposals.
JP-A No. 57-42578 shows the addition of a metal monoboride and at least one metal carbide, silicide, nitride or oxide. JP-A No. 58-55378 shows the addition of zirconium oxide. JP-A No. 60-103080 shows the addition of a compound boride of W and Fe, Co or Ni. JP-A No. 60-195061 shows the addition of molybdenum silicide. JP-A No. 61-97169 shows the addition of a metal monoboride and titanium carbonitride.
However, most of the above proposals require hot-press sintering to obtain sintered ceramics of good mechanical properties since the products of sintering under normal pressure are insufficient in deflective strength. Furthermore, TiB.sub.2 and/or ZrB.sub.2 base sintered ceramics proposed until now are generally insufficient in fracture toughness.